1. Field of the Invention
The present invention relates to a tensioner for an endless chain power transmission system. More particularly, to a chain tensioner system with a blade tensioner for imparting tension to a chain that drivingly connects a driven shaft to a driving shaft.
2. Description of Related Art
In an automotive engine, a blade-type tensioner has been used as a tensioner to impart tensioning force to an engine timing chain or a drive chain for an auxiliary such as an oil pump and the like. A blade-type tensioner is comprised of a blade shoe having an arcuately curved chain sliding surface and a leaf-spring-shaped blade spring provided on the opposite side of the chain sliding surface of the blade shoe to apply a spring force to the blade shoe. A proximal end portion of the blade shoe is rotatably supported around a supporting shaft inserted thereinto. A distal end portion of the blade shoe is slidably supported on a supporting surface provided discretely from the blade shoe.
In operation, a chain runs along the chain sliding surface of the blade shoe. A resilient force caused by deformation of the blade shoe and the blade spring presses on the chain, thereby maintaining the chain tensioning force.
When resonance occurs with the blade-type tensioner an adequate compressive force may not be applied to the chain by the tensioner, thereby causing tooth jumping of the chain. Tooth jumping will change the relative timing of the driving and driven shafts, and in some engines could cause valve damage or retard the ignition timing of the engine. Therefore, there is a need to prevent the blade tensioner from causing resonance in the normal rotational speed of the engine. In order to prevent resonance, the resonant frequency of the blade tensioner may be made higher than the usual rotational speed of the engine by enlarging the spring rate of the blade spring.
In a conventional blade tensioner however, when enlarging the spring rate by increasing the number of the blade springs or increasing the thickness of each blade spring, difficulties arise in assembling the blade spring in to the blade shoe. Therefore, in a prior art blade tensioner, it is not easy to improve the spring properties.